1. Field of the Invention
The present invention relates to an electronic device disposed or connected with an external storage device such as the SD (Secure Digital) memory card and, particularly, relates to an electronic device, a data transfer controlling method thereof, a data transfer controlling program thereof, a circuit chip, a circuit device, and a data transfer system that can use an interface function of USB (Universal Serial Bus), etc., to transfer data to an external storage device for writing of data.
2. Description of the Related Art
In a method of writing application data, etc., externally into an external storage device disposed on a portable terminal device such as a cellular phone, the portable terminal device is connected to a personal computer (PC) and the data to be written are loaded from the PC to the portable terminal device and written into the external storage device.
With regard to such data transfer, in the disclosure of Japanese Patent Application Laid-Open Publication No. 2005-130339, a cellular phone is connected to a PC to transfer image data, etc., (paragraph No. 0030, FIG. 1), and in the disclosure of Japanese Patent Application Laid-Open Publication No. 2005-123843, an communication device is connected to a PC through a USB cable, and image data, etc., in the communication device are transferred to the PC through the USB cable and stored (abstract, FIGS. 1 and 2).
By the way, if data are transferred from a PC to a portable terminal device disposed with an external storage device to write the data into the external storage device, the portable terminal device and the PC are connected with a USB cable, and the portable terminal device uses DBB-LSI (Digital Base Band—Large Scale Integration) constituting a modem to perform data transfer and data writing via so-called PC communication through the intervention of the modem.
When an electronic device is disposed with a single USB driver as is the case of the portable terminal device, a single interface (I/F) is connected to a USB cable and the data transfer tends to be complicated. If serial/parallel signals are used for an internal process of the portable terminal device in the data transfer, the rate of the data transfer is reduced due to the data length limitation and clock performance, and the writing time of the external storage device is limited.
Various types of data such as documents, images, videos, music, and game software are transferred from the PC to the external storage device of the portable terminal device, and it is indicated that transferring of an enormous amount of data such as video data or music data takes time.
Japanese Patent Application Laid-Open Publication Nos. 2005-130339 and 2005-123843 do not disclose or indicate such problems or a means for solving the problems.